The viability of microorganisms in preservation solutions

In 1988 the University of Wisconsin solution was introduced into clinical transplantation. This solution is unique in that it contains no glucose but rather raffinose, lactobionate, and hydroxyethyl starch. In addition, it contains two antibiotics, penicillin and bactrim. Prior studies have shown that other preservation solutions allow the transmission of bacterial contamination from organ donor to recipient. However, there are no data on whether UW solution, with its unique composition and extended preservation times, allows bacterial transmis-sion. We undertook the present study to establish if bacteria remain viable in UW solution at extended pres-ervation times. Cultures of both aerobic (Escherichia coli, Staphylo-coccus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa) and anaerobic (Bacteroides fragilis) bacteria were suspended at 10⁵, 10⁴, 10², and 10¹ org./ ml (calibrated from a.5 Macfarland turbidity standard) in both Eurocollins and UW preservation solutions. Samples were then stored in an ice bath to simulate organ preservation. The organisms were removed and plated on blood and chocolate agar at 0, 6, 12, 18, 24, and 36 hr postsuspension. The samples were then incubated at 37°C and read for growth at 24-48 hr after plating. Our results showed growth of all organisms except S epi in both preservation solutions, at all dilutions and preservation times. S epi grew in the Eurocol- lins solution at all dilutions and preservation times but did not grow in the UW solution. When the experiment was repeated omitting penicillin from the UW solution, S epi grew at all dilutions and preservation times. These results demonstrate that in spite of the inclusion of two different antibiotics, the majority of the common bacterial contaminants of the organ donor remain viable in UW solution with extended preservation times. It may be possible therefore to omit these antibiotics from the UW solution and obtain similar results. It is also important to note that routine culturing remains an expensive but necessary part of organ procurement and preservation.